Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Restricted Stock Activity) (Details)

v3.7.0.1
Stock-Based Compensation Plans (Restricted Stock Activity) (Details) - $ / shares
shares in Millions
12 Months Ended
May 31, 2017
May 31, 2016
May 31, 2015
Restricted Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested, Beginning balance, Awards 0.1    
Granted, Awards 0.1    
Vested, Awards (0.1)    
Forfeited, Awards    
Nonvested, Ending balance, Awards 0.1 0.1  
Nonvested, Beginning balance, Weighted-average grant-date fair value per share $ 43.99    
Granted, Weighted-average grant-date fair value per share 60.83 $ 47.46 $ 41.70
Vested, Weighted-average grant-date fair value per share 42.87    
Forfeited, Weighted-average grant-date fair value per share 48.61    
Nonvested, Ending balance, Weighted-average grant-date fair value per share $ 53.05 $ 43.99  
Performance Restricted Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested, Beginning balance, Awards    
Granted, Awards [1] 0.2    
Vested, Awards    
Forfeited, Awards    
Nonvested, Ending balance, Awards 0.2  
Nonvested, Beginning balance, Weighted-average grant-date fair value per share    
Granted, Weighted-average grant-date fair value per share [1] 53.74    
Vested, Weighted-average grant-date fair value per share    
Forfeited, Weighted-average grant-date fair value per share    
Nonvested, Ending balance, Weighted-average grant-date fair value per share $ 53.74  
[1] LTIP performance shares granted assumes achievement of performance goals at target. Actual amount of shares to be earned may differ from this amount.